Electronic components used in various electronic devices have recently been down-sized and multilayered, leading to a wide use of multilayer-type electronic components such as multilayer circuit boards, multilayer coils, and multilayer ceramic capacitors.
Multilayer ceramic capacitors, for example, are commonly produced by the following procedure. First, a solution of a binder resin, such as polyvinyl butyral resin, poly(meth)acrylic ester resin, or ethyl cellulose, in an organic solvent is blended with a plasticizer, a dispersant, or the like. The mixture is then blended with a ceramic raw material powder to give a ceramic slurry. Next, the ceramic slurry is casted on a surface of a supporting member preliminary subjected to a mold-release treatment. After removal of a volatile content, such as the organic solvent, by heating or the like, the resulting product is peeled from the supporting member to provide a ceramic green sheet.
To the ceramic green sheet, a conductive paste is applied by screen-printing for formation of an internal electrode. A plurality of such sheets are piled, and thermocompressed to give a lamination. Then, the lamination is subjected to a treatment for removing the binder resin contained therein by pyrolysis, namely, the lamination is degreased. The resulting lamination is fired to give a ceramic sintered body. On end faces of the ceramic sintered body, external electrodes are formed, thereby producing a multilayer ceramic capacitor.
A thinner internal electrode with a smoother surface is now demanded to be used in a smaller and higher-capacity multilayer ceramic capacitor. As a conductive paste for forming a thin and smooth internal electrode, for example, Patent Literature 1 discloses a conductive paste in which the particle size of a metal material is controlled so that the resulting electrode has a smooth surface.
However, the smoothness needs to be further improved in a recently desired thinner electrode layer. Even in the case where the particle size of a metal material to be used is controlled, if the metal material is not mixed well with other constituent materials of the conductive paste, such as an organic solvent or a binder resin, the dispersibility thereof is not enough, so as to hardly providing a printed electrode with a smooth surface.
Patent Literature 2 discloses use of a low-polarity organic solvent for preventing sheet attack against a ceramic green sheet.
However, a conventional polyvinyl acetal resin used as a binder of a conductive paste is hardly dissolved in the above-mentioned low-polarity organic solvent because of poor solubility of the polyvinyl acetal resin in the organic solvent derived from their difference in polarity, though the polyvinyl acetal resin, which can prevent delamination (interlayer peeling), is effectively used for preparation of a thinner electrode. The use of a conventional polyvinyl acetal resin in an electrode paste therefore lowers the dispersibility of inorganic powder to roughen the surface of a printed electrode, leading to difficulty in achieving smoothness.
As another problem, storage of a conventional conductive paste for a long time changes its viscosity, and such a paste is hard to use in the printing process.